Corrosion preventing apparatus and method

ABSTRACT

The present invention pertains to a splash zone coating system for the protection of metallic surfaces subject to active corrosion. More specifically, the present invention pertains to novel means for covering and coating metallic structures, e.g., pipe leg supports of an offshore oil well structure, from seawater corrosion in the splash zone of the structure which is that area subjected to intermittent contact by seawater.

United States Patent 1 Shaw et al.

[ 1 March 6, 1973 1 CORROSION PREVENTING APPARATUS AND METHOD [75}inventors: Clarence W. Shaw, Metairie; George R. Smith, Ponchatoula,both of La. [73] Assignee: Donald W. Durant, Covington, La.

by said Smith [22] Filed: Dec. 22, 1969 [21] Appl. No.: 873,755

[52] US. Cl ..61/54 [51 Int. Cl ..E02d 5/60, E04b 1/64 [58] Field ofSearch ..6l/54 [56] References Cited UNlTED STATES PATENTS 2,928,4113/1960 Johnson ..6l/54 X llllllllllunlllllullnnllunlihu IIIIIII 2 |unIIIIIII u" lllllllllll nu "In":

3,181,300 5/1965 Plummer ..6l/54 2,412,185 12/1946 Weber ..61/54 992,7765/191 1 Hubbard ..61/54 X Primary Exagniner.la cob Shapiro Att0mey-HarryW. F. Glemser, Leo A. Rosetta, J. William Pike, Jesse B. Grove, Jr. andFrancis D. Thomas, Jr.

[ 5 7 ABSTRACT 5 Claims, 3 Drawing Figures DJ 5 N I 5 12 I r .J a. j m

PAIENIEnHAReIm FIG. 3

CLARENCE W. SHAW GEORGE R. SMITH BY: (29% ATTORNEY S R O T N E V N FIG.2

CORROSION PREVENTING APPARATUS AND METHOD BACKGROUND OF THE INVENTIONThe present invention pertains to that field of the art concerned withmeans for protecting a metallic surface subject to active corrosion bythe intermittent wetting and/or splashing of water. More particularly,the present invention is concerned with the combination of novel meansfor covering a metallic surface subject to the corrosive action ofseawater whereby the surface is constantly treated with a rustinhibiter.

A metallic structure erected in water is subject to considerablecorrosion especially in those instances where the water has any degreeof salinity. That part of such a structure subjected to the intermittentor frequent contact of water, either due to splashing or by tidalchanges, experiences the most severe corrosion. This zone which isnormally referred to as the splash zone, is defined as that existingbetween the highest point reached by the water due to either wave actionor splashing, to the lowest point reached by air. Corrosion in thissplash zone is usually most severe and difficult to protect. As is wellknown, for surfaces located above the splash Zone, various well knowncorrosion systems can be employed, e.g., conventional paints, plasticcoatings, and the like. Below the splash zone, corrosion can beeffectively combated by cathodic protection.

There are various well known techniques and/or means for protecting ametallic structure, such as an oil well rig, from the effects of activecorrosion caused by seawater which mainly attacks the supports of thestructure that are located in the splash zone. For example, in the caseof offshore oil rigs, their steel pilings, pipe legs, or conductor pipescan be coated with a sacrificial metal layer over its length definedwithin the splash zone. Or, such a surface can be covered over with arust resistant metal coating. In either case, it can be appreciated thatthe initial expense of the rust resistant coating or the subsequentmaintenance of the sacrificial coating is costly. The present inventionprovides a relatively inexpensive manner of covering such surfaces asabove described whereby they can be constantly subjected to corrosionproofing by well known rust inhibitors. Further advantages and featuresof the present invention will become apparent as the discussionproceeds.

SUMMARY The present Splash Zone Coating System basically comprises aflexible membrane adapted to operably fit over and around the surface ofa metallic structure over its area that is subjected to intermittentcontact of water. The flexible membrance defines a cavity between itsinner surface and the surface of the metallic structure. Closure meansare provided which is attached to the flexible membrane whereby themembrane can be conveniently attached to, over, or around the metallicstructure. Sealing means operably connected to the flexible membrane areprovided for sealing the flexible membrane to the metallic structure. Asuitable rust inhibitor is injected into the cavity defined by theflexible membrane whereby the surface of the metallic structure is keptconstantly coated with the inhibitor.

Preferred embodiments include means for filling and venting the flexiblemembrane, as well as means for attaching the membrane to a cylindricalsurface to be protected.

DESCRIPTION OF THE DRAWING FIG. 1 in the drawing represents an elevationview of a preferred form of the present invention as adapted forprotecting a cylindrical structure.

FIG. 2 represents a sectional view taken along the line AA of FIG. 1showing the cavity created between the flexible membrane and the surfaceto be protected from corrosion by a surrounding aqueous environment.

P16. 3 depicts a partial sectional view taken along the line BB of FIG.1 showing a preferred manner of sealing and protecting the end portionof the flexible membrane as it is adapted to fit around and protect acylindrical structure.

PREFERRED EMBODIMENT The present Splash Zone Corrosion proofing means 10comprises the flexible membrane H which as shown in FIG. l is adapted tofit over and around the external surface of a specific metallicstructure to be protected. The wrapper or jacket 11 is made of aflexible material that is capable of withstanding the elements.Additionally, the wrapper 10 is preferably a tenacious material capableof withstanding battering by vessels or objects floating in the water. Afabric reinforced synthetic rubber, such as neoprene, or achlorosulfonated polyethylene, are preferred materials of construction.However, many other types of flexible materials can be employed as longas they are compatible with the elements and the rust inhibitor employedin the cavity between the wrapper and the metallic structure.

The jacket 11 is preferably provided with the slide fastener means 12which extends along its edges parallel to the longitudinal axis of theoil rig pipe support R3. The slide fastener means 12 can be any suitableheavy duty slide fastener closure means which is essentiallywater-tight. Such means are well known and available in the art. Theslide fastener means 12 can be either glued to the membrane 11 or sewnthereto with nylon thread or the like. 7

As shown in FIG. 2, the flexible member 11 and the metallic structure 13form the cavity or annulus 14 therebetween. In the installation of theassembly 14, a suitable rust inhibitor is injected into the cavity 14 inthe manner described hereinafter. The rust inhibitor can be any suitablematerial that is capable of floating on water and which has a higheraffinity for metal than water. In such manner, the material will coatthe metallic surface of the membrane 13 forcing the water away. Theinhibitor is preferably a petroleum base hydrophobic cationic materialwhich is readily available in the art. These materials are generallyblack liquids which combine mineral oils with wetting agents and rustinhibitors. Such materials will generally penetrate existing rust anddisplace water; adhere to and give full protection to either wet or drysurfaces; will not dry out, harden, or crack; they float as a liquidlayer on top of water; and resist water washing once applied.

The present corrosion proofing means also preferably comprises the inletvalve assembly which is operably connected to the member 1 1 in anyconventional or well known manner. For example, the wrapper 11 can beprovided with a rubber jacketed conduit connector that is glued or sewnto the wrapper 11. Thereafter, a suitable hand operated valve isattached for achieving the mode of operations brought out below. Thevalve outlet assembly 16 is also preferably provided and which functionsin a similar manner as the assembly 15. Likewise, it can be operablyconnected to the jacket 11 in a similar manner. The valve portion of theassembly 16 preferably comprises a flow check valve whereby any materialin the cavity 14 can flow outwards at any time to avoid rupturing of thewrapper 11 due to over pressurization, yet avoid the re-entry ofseawater, as well as acheive the mode of operation described below.

As shown in 'FIG. 1, the jacket 11 is also preferably provided with theinlet slit or opening 17 which in turn preferably further comprises azipper construction 18 sentially equal to that of the surrounding water.A rust inhibitor is then added to the cavity 14, preferably via similarto the slide fastener means 12. The inlet 17 is provided forinjecting orpouring the liquid rust inhibitor into the cavity 14. However, the inlet17 can be dispensed with and the rust inhibitor injected in the cavity14 via the valve assembly 15. Such an operation would naturally requiremore expensive equipment, consequently, the separate filling opening 17is preferred.

Referring to FIG. 3, the flexible membrane 11 is preferably providedwith the additional section 18 which is generally made up of the samematerial of constructionas the membrane 11."The resilientmember 19,preferably a sponge rubber, is provided so as to foem a seal between themembrane 11 and the external surface of the metallic structure 13. Theresilient member 19 in combination with the portion 18 define the radialwidth of the cavity defined between the members 11 and 13.The member 18also serves to reinforce the end portion, generally over a width ofabout 4 inches, from the mechanical forces induced by the strap means20. The strap means 20 is preferably a corrosion resistant material,e.g., monel, stainless steel, or thelike, which is banded around the endportion of the membrane 11 and operably clinched in position by use ofvarious well known banding devices. Of course suitable screw operatedclamping devices could be emplayed in lieu thereof. Moreover, theassembly could actually be glued into position with a suitable adhesive,such as an epoxy resin, or the like.

In operation, the flexible membrane 11 is first wrapped around thesurface to be protected which is that area generally known as the splashzone. The slide fastener 12' is then brought together and thewrapper llfastened tight, for further protection the end portions are wrapped witha heavy tape, e.g., polyethylene, or the like. The band or strap means20 is then applied. In such manner, theassembly l0 formsthe enclosedcavity 14 between the external surface of the member l3and the innersurface of the membrane 11. Since a part of the jacket 11 will extendbeneath the surface of the water, it is necessary toemploy a diver tosecure and clamp the lower portion.

When the jacket 11 is initially placed into position and fastened shut,water will natrually be trapped the opening 17 after which the slidefastener 18 is closed.

Next, compressed air or some other suitable medium is then introducedinto the jacket 11 by through of the valve assembly 15. The pressurizingmedium need only be of sufficient pressure to force the water out of thecavity 14 through the exit valve assembly 16. In other words, thepressure must be sufficient to overcome the head established by thedepth to which the valve assembly 16 is immersed beneath the surface ofthe water. The pressure forces the rust inhibitor to flow down and coatthe steel to the depth established by the valve assembly 16. The valveassembly 16 being a check valve, allows the water to flow out, yetprevents back-flow thereafter.

I The source of pressure is then cut off and disconnected from the valveassembly 15. Where the member 11 is tightly sealed to the structure 13,the valve assembly 15 should preferably thereafter be opened to theatmosphere. This allows the rustinhibitor to rapidly return upwardsdepending upon the amount of leakage back into the cavity 14. It can beappreciated that if and when water does force itself back into thecavity 14, the above sequence of operations can be repeated at desiredintervals which again coat the surface of the structure 13. Recoating ofthe metallic surface can also be effectuated by massaging the wrapper 11with a suitable means such as a garter spring. The massaging action willalso naturally occur as the water level outside of the jacket risesabove the water and rust inhibitor level inside the jacket whereby theoutside water pressure will squeeze the jacket against the structure 13.This action forces these fluids within the space 14 to rise. V It willbe apparent to one skilled in the art that considerable changes andmodifications can be made in the above described embodiment of ourinvention without departing from its true scope and spirit. For example,the wrapper 11 can be made in a number of separate parts, all of whichcan be zippered together to form the .desired diameter of wrapper.Moreover, the wrapper 11 could be binded to the structure 13 in diversemanners. Additionally, where the splash zone is defined over aconsiderable length, a series of superposed or stacked jackets 11 couldbe utilized.

We claim:

1. Means for corrosion proofing a metallicstructure subject tointermittent contact by seawater, said means comprising:

a. a flexible membrane covering themetallic structure over that areasubjected to intermittent contact by seawater so as to define a cavitybetween said flexible membrane and the metallic structure; a body of awater immiscible liquid rust inhibitor, lighter than water, in but notcompletely filling-the cavity whereby the said area of the metallicstructure will be periodically completely coated by the rust inhibitorupon the rise and fall of the seawater due to wave action and/or tidalchanges andthe resulting flexure of said membrance;

b. closure means fixedly attached to said flexible membrane and metallicstructure and sealing off the portion of the metallic structure subjectto intermittent contact by seawater; and

c. sealing means for sealing the ends of said flexible membrane to themetallic structure.

2. The corrosion proofing means of claim 1 further characterized ascomprising:

d. filling means attached to said flexible membrane adjacent the topthereof whereby said water immiscible liquid rust inhibitor can beinjected in the cavity defined between said flexible membrane and themetallic structure.

3. The corrosion proofing means of claim 2 wherein:

e. said filing means comprises inlet valve means connected to saidflexible membrane whereby the cavity defined between said flexiblemembrane and the metallic structure can be pressurized; and

f. outlet valve means connected to said flexible membrane adjacent thebottom thereof for venting the cavity defined between said flexiblemembrane and the metallic structure.

4. The method of corrosion proofing a metallic structure subjected tointermittent contact by sea water at the surface of a body of saidwater, comprising the steps of:

establishing a zone around said structure, by flexible confining means,at said seawater surface of a size to extend throughout the range ofchange of level of said surface;

confining a body of liquid, water-immiscible corrosion inhibitingmaterial in said zone within said confining means and in contact withsaid metallic structure;

excluding sea water from said zone; and

maintaining said confining means in contact with said body of water atsaid surface whereby movement of sea water at said surface distorts saidconfining means and the outer boundary of said zone and thereby agitatesand produces flow of said corrosion inhibiting material along thesurface of said metallic structure.

5. The corrosion proofing means of claim 1 further characterized in thatsaid flexible membrane comprises a rubber-fabric composition.

1. Means for corrosion proofing a metallic structure subject tointermittent contact by seawater, said means comprising: a. a flexiblemembrane covering the metallic structure over that area subjected tointermittent contact by seawater so as to define a cavity between saidflexible membrane and the metallic structure; a body of a waterimmiscible liquid rust inhibitor, lighter than water, in but notcompletely filling the cavity whereby the said area of the metallicstructure will be periodically completely coated by the rust inhibitorupon the rise and fall of the seawater due to wave action and/or tidalchanges and the resulting flexure of said membrance; b. closure meansfixedly attached to said flexible membrane and metallic structure andsealing off the portion of the metallic structure subject tointermittent contact by seawater; and c. sealing means for sealing theends of said flexible membrane to the metallic structure.
 2. Thecorrosion proofing means of claim 1 further characterized as comprising:d. filling means attached to said flexible membrane adjacent the topthereof whereby said water immiscible liquid rust inhibitor can beinjected in the cavity defined between said flexible membrane and themetallic structure.
 3. The corrosion proofing means of claim 2 wherein:e. said filing means comprises inlet valve means connected to saidflexible membrane whereby the cavity defined between said flexiblemembrane and the metallic structure can be pressurized; and f. outletvalve means connected to said flexible membrane adjacent the bottomthereof for venting the cavity defined between said flexible membraneand the metallic structure.
 4. The method of corrosion proofing ametallic structure subjected to intermittent contact by sea water at thesurface of a body of said water, comprising the steps of: establishing azone around said structure, by flexible confining means, at saidseawater surface of a size to extend throughout the range of change oflevel of said surface; confining a body of liquid, water-immisciblecorrosion inhibiting material in said zone within said confining meansand in contact with said metallic structure; excluding sea water fromsaid zone; and maintaining said confining means in contact with saidbody of water at said surface whereby movement of sea water at saidsurface distorts said confining means and the outer boundary of saidzone and thereby agitates and produces flow of said corrosion inhibitingmaterial along the surface of said metallic structure.